1. Field of the Invention
The present invention relates to an air cutoff valve, and in particular to an air cutoff valve and a restart stabilization method using the same which provide a quick restart by maintaining an open state of a flap valve for the sake of an air supply even when an engine stops unintentionally, and which provide a reduced number of molding processes and an enhanced productivity along with a reduced manufacture cost in such a way to apply a plastic material to elements.
2. Description of Related Art
A fuel cell vehicle necessitates air for the sake of a hydrogen reaction in a fuel cell stack, and the amount of air needed for a hydrogen reaction should be controlled.
A motored blower is generally used so as to suck and supply air, and an ACV (Air Cutoff Valve) is used for controlling the flow rate of air.
FIG. 9 is a view illustrating an air system line of a conventional fuel cell vehicle.
As shown therein, the air system line is connected with an inlet line 300 by way of which the sucked air flows to a fuel cell stack 200. An outlet line 40 is connected to the air system line for the air to discharge. A humidifier 500 is installed at the inlet line 300 and the outlet line 400 for the purpose of humidifying the air.
The blower 60 is installed at the inlet line 300 at the rear end of a filter 610 configured to filter the sucked air. The ACV 70 is installed at not less than one portion of the inlet line 300 and the outlet line 400 to make sure that the durability of the fuel cell stack 200 can be protected.
As described above, the ACV 700 is a member for the purpose of adjusting the air flow rate during the hydrogen reaction and comprises a housing body 701 with a certain air passage for the sake of air flow, a motor 710 having a driver generating a driving force in response to a control signal from a controller, a flap valve 720 configured to vary the opening degree with respect to an air passage of the housing body 701 using the flap body 722 rotating together with a rotary shaft 721 while the motor 710 is driving, and an electronic valve 730 controlling the motions of the flap valve 720 as it receives a rotational force from the motor 710.
The vehicle might stop as a driver keys off the engine under a normal situation that the driver intended or it starts as the driver keys on the engine or the vehicle might stop as the engine stops unintentionally in an abnormal situation. When the engine stops in an abnormal situation, a quick restart enhances the restart operation, thus enhancing the quality and reliability of a product.
Since the restart of an engine necessitates an air supply by way of the ACV 700 like when the vehicle first starts, the ACV 700 supplying the air is the most basic factor determining an engine start condition in terms of the engine start stability of the fuel cell vehicle.
The above explained ACV 700 is weak in terms of the restart performance of an engine.
The above mentioned problem is thanks to the operation type of the ACV 700. The ACV 700 operates in such a way that the flap valve 720 is switched to the full close state irrespective of the normal or abnormal operation when the engine is in a key off state, whereas the flap valve 720 is switched to the full open state in case of the key on.
Even though the engine stops, which is not a driver's intention, the operation state of the ACV 700 switches in a sequence of “the full open→full close”, the procedure of which represents that even though the driver quickly restarts the engine, it switches in a sequence of “the full close→full open” like the first engine start situation.
The ACV 700, which does not have a good response performance to a driver's quick restart demand, makes impossible a quick restart, so the vehicle stopped due to the unexpected engine stop cannot be quickly moved. The driver might have an increasing worry. In worse case, the reliability of the vehicle becomes bad.
The ACV 700 comprises an integrated housing body 701 configured to accommodate the motor 710 at one side and the electronic valve 730 at the other side to cooperate with the motor 710 and the flap valve 720, so the housing body 701 has disadvantages in terms of the manufacture of the ACV 700.
For example, the ACV 700 is manufactured in such a way that the housing body 701 is injection molded by die casting a conventional aluminum material, and holes are formed, and the surface of it is processed, and bearings are engaged in the housing body 701 along with other elements, and a cooling tube is inserted for the sake of the circulation of cooling water.
When the ACV 700 is manufactured, the housing body 701 inevitably becomes heavy because the aluminum is used, and the thermal durability of the ACV 700 becomes lowered due to the thermal expansion of the aluminum material.
In particular, the thermal sensitivity of the ACV 700 might be a cause which brings an abnormal operation when the cooling performance becomes bad, so the ACV 700 might affect the quality and the reliability of the fuel cell vehicle adapting the same.
The ACV 700 is manufactured using an aluminum material, the molding of the housing body 701 is limited to the die casting method, which results in an inconvenient molding, and such inconveniences increases more in the next assembling process following the molding.
For example, it is manufactured in a sequence that an aluminum material is die-cast, and the whole profile of the housing body 701 is injected, and the holes are formed, and surfaces are processed, and then the related elements are assembled, thus finishing a product; however the above mentioned molding and assembling procedures are complicated, which causes the manufactures of the ACV 700 to slow.
The ACV 700 adapting the housing body 701 made from an aluminum material is not good at a rust inhibition for the fuel cell vehicle which is exposed to relatively more moistures.
The above mentioned phenomenon becomes worsened since the ACV 700 closes when the engine stops, and the water produced from the fuel cell stack 200 could not leak to the outside and gathers instead at the side of the ACV 700.
The water at the ACV 700 causes an unstable cold start due to the freezing of moisture under a below-zero external temperature condition. The aluminum might be corroded due to moisture.
The solidification of the flap valve 720 due to the freezing of the moisture of the ACV 700 can be easily melted and resolved using the heater; however the corrosion phenomenon cannot be removed unless moisture is fully eliminated.
When the ACV 700 is more corroded due to the moisture, the water might be leaked to the electronic elements such as the electronic valve 730 controlling the flap valve 720 or the motor, so the ACV 700 might be failed.